If you want to have some fun, you can register an AR-15 with the Canadians and take it across the border.
Takes about nine months to get all the paperwork done, but it is entirely possible to do.
I've never had a problem transporting rifles and shotguns into or through Canada. Used to be able to transport handguns that customs would seal in a plastic bag.
I’d just like to FIND an AR-15 at this point.